This trial is active, not recruiting.

Summary

A crossover trial with healthy volunteers will be conducted. Three sessions will be
performed with at least 48 hours washout period to minimize carry-over effects. In each
session, volunteers will be submitted to: fatigue and attention levels evaluation,
handwriting test, serial reaction time task (SRTT) before and after ctDCS conditions and
after session, a performance perception evaluation.

Current will be applied by a DC stimulator (NeuroConn Plus, Germany).The active electrode (anode: 5x7 cm²) will be placed over the left cerebellar hemisphere (3 cm lateral to the inion) and the reference (5x7 cm²), over the left arm with current intensity of 2mA, fade in and fade out of 10 seconds, during 20 minutes.

Current will be applied by a DC stimulator (NeuroConn Plus, Germany). The active electrode (cathode: 5x7 cm²) will be placed over the left cerebellar hemisphere (3 cm lateral to the inion) and the reference (5x7 cm²), over the left arm with current intensity of 2mA, fade in and fade out of 10 seconds, during 20 minutes.

Sham ctDCS (NeuroConn Plus, Germany) will be applied at the same parameter settings used on cathodal ctDCS however, current duration will be only 30 seconds. Moreover, device automatically turned off without volunteer's perception, but volunteers will be with electrodes montage for 20 minutes.

Primary Outcomes

Measure

Changes on implicit motor learning

time frame:
One week (before and after ctDCS)

Secondary Outcomes

Measure

Changes on fatigue levels

time frame:
One week (before and after ctDCS)

Changes on attention levels

time frame:
One week (before and after ctDCS)

Changes on explicit motor learning

time frame:
One week (before and after ctDCS)

Eligibility Criteria

Male or female participants from 18 years up to 40 years old.

Inclusion Criteria:
- Right-handed (assessed by Edinburgh Handedness Inventory)
- Healthy volunteers (self report)
- Absence of neurological and psychiatric diseases
- No history of severe musculoskeletal injury on wrists and fingers
- Without using drugs or neuroactive substances regularly
Exclusion Criteria:
- Pregnancy
- Presence of metallic implant in close contact to the target stimulation area
- Acute eczema under the target stimulation area
- Pacemaker
- History of seizures or epilepsy
- Hemodynamic instability

Additional Information

A crossover, pseudo-randomized, sham-controlled and triple blind will be performed in order
to evaluate ctDCS effects on motor learning, since evidence pointed to the crucial role of
cerebellum on motor behavior. A non-involved research will conduct a pseudo-randomization
(www.randomization.com) to warrant the counterbalanced sessions order and the allocation
concealment. Volunteers, researchers and statistical analysis will be blinded to ctDCS
condition.
After given prior informed consent, volunteers will be submitted to three experimental
sessions: anodal ctDCS, cathodal ctDCS and sham ctDCS. Fatigue and attention levels,
handwriting test and SRTT will be performed before and after stimulation. In addition,
performance perception evaluation will be assessed at the end of session.
Electrical current will be delivered through a DC stimulator (NeuroConn Plus, Germany) using
a pair of saline-soaked sponge electrodes (surface 35cm²). The active electrode (anode or
cathode) will be placed over the left cerebellum (3 cm lateral to the inion) and the
reference, over the left arm with current intensity of 2mA, fade in and fade out of 10
seconds, during 20 minutes. Sham tDCS has been used in several studies to evaluate active
tDCS effects.
Sham ctDCS will be applied using the same electrodes placement and parameter settings of
cathodal ctDCS however, stimulation will last only 30 seconds but volunteers will be with
electrodes montage for 20 minutes. Because the device will be automatically turned off
without volunteer's perception, early sensations (mild to moderate tingling) on stimulation
site will be experienced without inducing any modulatory effects. Moreover, after each ctDCS
session, an adverse effects questionnaire will be applied.
Fatigue and attention levels will be measured through an analogue scale graded from 0 to 10,
where 0 means lower fatigue or attention levels and 10, the higher fatigue or attention
levels.
Handwriting test: volunteers will be instructed to write six words with digital pen using
the non-dominant hand on a tablet provided with analysis software system (MovAlyzer, EUA).
The task will be performed spontaneously, without any instruction bias during writing
activity. Each session has different word sequences but the difficulty level will be
maintained (six words, two of them with 4, 6 and 8 letters).
SRTT: will be performed through software with visual stimuli presented on a computer screen
in four different positions. Volunteer must press, with the non-dominant hand, a
corresponding key with a predetermined finger as soon as possible when a highlighted star
appears on the screen. The test comprises eight blocks with 120 trials each. Implicit motor
learning is measured by performance changes between the blocks 5, 6 and 7.
Performance perception evaluation: in order to correlate stimulation type to the conscious
improvement on motor task performance (SRTT and handwriting test) will be asked in the end
of each session: "Regarding today's session, comparing your motor performance before and
after cerebellar stimulation, you consider that you were better, worse or the same as
before?"